With the method of estimating the lifetime of a semiconductor device and a semiconductor power converter described in patent document (PD) 1, a temperature detector is connected to the base plate of an IGBT element of an inverter and the number of ripple temperatures is counted in each temperature range.
With the elevator controller described in patent document (PD) 2, a lifetime assessment method is not addressed, but a loss per chip is calculated from, for example, an output signal from a current detector to prevent the chip from causing a thermal runaway due to a junction temperature rise in an IGBT element.